Many hydraulic systems have a large capacity pump as the primary source of fluid for several control valves each of which controls fluid flow to one or more fluid motors. In some systems, a smaller capacity pump supplements the output of the larger pump until the fluid pressure of the system reaches a predetermined magnitude. One of the problems encountered with such systems is that, although the output of the small pump generally is needed for only the motor or motors controlled by one control valve or for only a small percentage of the time, the output of both pumps passes through the control valves when the fluid pressure is below the predetermined magnitude. This causes additional problems, particularly when fluid flow to the motors is being modulated by the control valves since the control valves must modulate the total output of both pumps and must be sized accordingly.